Detection of ultraviolet (UV) radiation is an important feature for many applications. Sensitive UV light detection may find applications as diverse as military, security, commercial, and consumer applications.
UV detection may make use of the photoelectric effect of metal and the gas multiplication effect. Many commercial UV detectors take the form of gas tubes. These are unsuitable in many cases due to slow response time, size constraints, and due to the demanding environments in which UV detectors, in some cases, may find utility. Semiconductor UV detectors have been developed in response to these problems. The semiconductor UV detectors are resilient and compact. Known commercial UV semiconductor detectors are formed from wide bandgap semiconductors.
Wide bandgap semiconductors used in conventional UV detectors include metal zinc oxide (ZnO) and magnesium zinc oxide (MgZnO). There are also Schottky-type TiO2 UV-photodetectors. Familiar III-V materials used in UV detectors include GaAs, GaP, and ternary AlGaAs and InGaAs. A distinctive aspect of Group III-nitrides is that their bandgaps are tunable within the energy range that corresponds to blue and ultraviolet wavelengths. Other approaches for UV detection include organics and phosphors.
Silicon based UV detection utilizes amorphous silicon alloys and silicon carbide material. Elemental silicon is not generally useful for UV detection because it has a bandgap of 1.1 eV, corresponding to an infrared wavelength of 1.1 μm. Si is accordingly not fit for UV detection, necessitating the use of other materials, such as nitride-based heterostructures grown on incompatible substrates, namely Si and Ge. Fabrication on Si leads to a large number of defects, which can impact device sensitivity and general performance. There is accordingly a need for an efficient UV detector that is compatible with pervasive silicon-based integrated circuit technology.